More US Republicans now have a negative view of the FBI than a positive one, a new poll has revealed, in a sign that Trump's criticism is making an impact.

An online poll found 47pc of Republicans have an "unfavourable" opinion of the FBI while only 38pc see it favourably.

It comes as a four-page document, written by Republican congressmen with access to confidential information, was released last Friday with Trump's approval.

Republicans have pounced on the memo's claim that senior justice and FBI officials acted improperly when securing a wire-tap on a Trump campaign aide as proof of political bias.

The FBI in turn expressed "grave concerns" about the memo and called it inaccurate and incomplete. Democrats said it was a set of cherry-picked claims aimed at smearing law enforcement and that releasing the memo would damage law enforcement and intelligence work.